A hydraulic gerotor device includes a stator having internal teeth and a rotor having external teeth. The rotor is mounted eccentrically within the stator. There is one more internal tooth on the stator than external teeth on the rotor. The internal teeth of the stator can be formed by cylindrical rollers, which can rotate to reduce wear in the gerotor device between the rotor and the stator.
The cylindrical rollers fit into roller pockets found in the stator. Pressurized chambers are formed between the rollers and the rotor. About one half of the chambers are filled with hydraulic fluid under high pressure and the remaining half are filled with hydraulic fluid under lower pressure. The engagement between the rollers and the rotor must provide sealing at two positions; namely, at the two points of separation between a high-pressure chamber and an adjacent low-pressure chamber.
One point of separation between the high-pressure and low-pressure chambers is formed by one roller contacting the peak of an external tooth of the rotor. This roller is subjected to an especially high loading. This roller is not only pressed into its pocket by the rotor, but also the pressure of the high-pressure chamber acts on the roller. In this situation, in some known gerotor devices the bearing surface area between the roller and the pocket is diminished so that a higher pressure is exerted on the roller. This higher pressure can be detrimental and can lead undesirable impressions being made in the roller or on the external tooth of the stator because the roller may no longer be rotating. This resultant wear over time impairs the sealing ability of the gerotor device